Fiach is an Irish male given name. It may refer to:

• Saint Fiacc, fifth-century bishop of Sletty in Ireland
• Fiach McHugh O'Byrne (1534–1597) Irish chief
• Fiach Mac Conghail (born 1964) Irish theatre director and Senator
• Fiach Moriarty, Irish singer-songwriter

• Tomás Ó Fiaich, Irish Catholic primate and cardinal

• Fiacha
• Fiachra
• Fiachna

This page or section lists people that share the same given name.
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